What kind of material is this cooktop made of?

glass

ceramic

platic

glass-ceramic

Glass-ceramic materials share many properties with both non-crystalline glass and crystalline ceramics. The negative thermal expansion of the crystalline ceramic phase can be balanced with the positive expansion of the glassy phase. At a certain point (~70% crystalline) the glass-ceramic has a net expansion near zero and can sustain repeated and quick temperature changes up to 1000 °C.